Vehicles, such as rail vehicles, include power sources, such as diesel engines. In some vehicles, fuel is provided to the diesel engine by a common rail fuel system. In the common fuel rail system, fuel injectors inject fuel from the common fuel rail to cylinders of the engine for combustion. Some engine systems may use an injector map stored within a memory of a controller to determine a fuel injector activation output. In one example, the fuel injector activation output may include an injector activation time, and/or an amount of time the injectors are injecting fuel into the engine cylinders. The injector map may include a table of injector activation data with each injector activation time corresponding to a fuel rail pressure and a fuel value, or quantity of fuel injected by a single fuel injector stroke. Thus, by using the injector map, an engine controller may output an injector activation time for a given fuel value and measured fuel rail pressure. Fuel injection may then be adjusted, based on the determined injector activation time, to deliver the desired amount of fuel to the engine cylinders.
The injector map described above may include a finite number of data points. Thus, in one example, the exact measured fuel rail pressure and desired fuel value may not be included in the injector table. As a result, the engine controller may interpolate between data points above and below the desired points to determine the injector activation time.
However, linearly interpolating between available fuel rail pressure values and fuel values in the injector map may result in interpolation error. Specifically, indexing the injector map by rail pressure may result in a non-linear relationship between fuel injector activation data. Therefore, linearly interpolating non-linear data may result in interpolation inaccuracies, thereby increasing fuel injector activation time error. This may in turn decrease fuel consumption efficiency and increase emissions variation.